10/20 Recording System


4 major landmarks

  • The Nasion – the indentation on the bridge of the nose between the eyes
  • The Inion – the midline bump on the inferior occipital bone near the junction of the cranium and spine
  • 2 peri-auricular notches – notches near the tragus of the anterior ear

3 fundamental lines that all other 10/20 sites are derived from:

  • 10% line – the circle line measured around the head 10% up from each of the 4 landmarks
  • C line – the line measured from the L and R peri-auricular notches
  • Z line – the line measured from the nasion to inion

frontal 1020

Frontal view

  • Shows the 10% measured from L and R peri-auricular notches.
  • Shows the C-line formed by the coronal plane

lateral 1020

Lateral view

  • Shows the 10% measurement from the nasion and inion
  • Shows the Z line formed int he saggital plane

superior 1020

Superior view

  • An axial view of the 3 fundamental lines and electrode sites of the 10/20 system

Detailed measuring of the 10/20 system is a very important component of accurate EEG recordings.  When electrodes are properly placed according to the 10/20 system, the coverage of the hemisphere is symmetrical.  If the electrodes are not symmetrically placed asymmetries may occur during recording.

Brain AreaL hemisphereMidlineR hemisphere
Frontal PoleFp1FP2
Frontal F3F4
Inferior FrontalF7F8
Anterior TemporalT1T2
Posterior TemporalT5T6
Vertex or Mid-centralCz
Non Scalp Leads


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